Telegraph system



M y 30, 1944- A. G. MILLER 2,350,180

TELEGRAPH SYSTEM Filed 001;. 17, 1942 L11, 1 LT INVENTOR Z G, f/filler ATTORNEY Patented May 30, 1944 UNITED STATES rarest orrics TELEGRAPH SYSTEM Arthur Gordon Miller, Staunton, Va., assignor to American Telephone and'Telegraph Company, a corporation of New York Application October 17, 1942,,Scria-l No.,462,338

3 Claims.

circuit. It has been found, that if one of the telegraph lines connected to the hub. circuit remains open it might put all of the other lines connectedzto. the hub circuit out of commission and; prevent transmission from taking place be-- tween said other. lines until the first disabled line is repaired. A type of telegraph circuitcnwhich the aforementioned kind of trouble might occur would be a difierential duplex system. In accordance with this invention arrangements are provided associated with the hub circuit whereby, if one of the lines connected thereto goes open and remains so for an appreciable period, it will automatically be disconnected from the hub circuit and transmission may take place between the remaining lines connected thereto. This will prevent undue interruption of the service. Other objects and features of the invention will appear more fully from the detailed description of the invention hereinafter given.

The invention may be more fully understood from the following description together with the accompanying drawing in which is shown a circuit diagram embodying a preferred form of the invention.

In the drawing are shown a plurality of telegraph lines L1, L2 and Lo terminating at the telegraph repeaters R1, R2 and R3. These are interconnected through a well known form of hub circuit 1. While only three lines have been shown interconnected by the hub circuit it is obvious that other lines could also be interconnected thereby. The telegraph repeater R1 would have a receiving relay RRi and a sending relay SR1. The telegraph repeater R2 would have a receiving relay RR2 and a sending relay SR2 and the telegraph repeater R3 would similarly have a receiving relay RRs and a sending relay SR3. With the arrangements as shown, namely when a marking signal is on line L1, equal negative batteries connected to each of the sending relays SR1, SR2 and SR3 will be connected to each end of the hub circuit and no current will flow thereover. This type of circuit is called an inverse neutral hub circuit. If a spacing signal is now received from line L1 relay RR1 will release and its armature will be connected over its spacing contact to ground. This ground will be applied over conductor 2 to the conductor 1 of the hub Lil circuit and thence over conductors 3 and l to the negative batteries connected to the windings of sending relays SR2 and SR3 andwill cause them to operate to send a spacing signal out over lines L2 and Lo. The next. marking signal to come in over line L1 will cause relays SR2 and SR: to

return to the marking position. If one of thelines, such for example as L1, became open and remained'so relay RRi would move to spacing and gro'undwould be permanently applied to its spacing contact. and. a continuous spacing signal would be sent out over lines L2 and L3. would prevent transmission between linesL2 and Liv and put them out of service as long as line L1 remained open.

As heretofore pointed out the arrangements of the invention provide additional apparatus in connection with the hub circuit whereby if one of the lines, such as L1, becomes and remains open it may automatically be disconnected from the hub circuit and service continued between the other lines, such as L2 and L3, connected to the hub circuit. This apparatus comprises a relay 8 which is connected to the hub circuit and hence is common to all of the lines. This relay is adjusted to be slow operative and hence will not operate on the ordinary spacing signal but will operate if any one of the lines remains open for an appreciable period. A series of relays 5, '6 and I, one for each line, is also provided to disconnect a disabled line from the hub circuit.

The operation of the arrangements of the invention is as follows. Relay 8 is normally unoperated because battery 9 in circuit therewith has its negative pole connected to the hub circuit. As the batteries connected to sending relays SR1, SR2 and SR3 have their negative poles connected to the hub circuit the voltage of these batteries, which is the same as that of battery 9, will oppose that of battery 9 and no current will flow in the hub circuit. If one'of the lines, such as L1, now becomes open, ground will be applied from the spacing contact of receiving relay RBI, to conductors 2 and I, winding of relay 8 to battery 9 and ground. If line L1 remains open for an appreciable length of time the slow operate relay 13 will operate. This will apply ground over the contact and armature of relay 8, conductor l2, conductor I3, right hand windings of relays 5, 6 and l, conductor H to battery 10 and ground. This will operate relays 5, 6 and i. As ground is connected to conductor 2 relay 5 will immediately lock up over a circuit completed over its armature and contact and left hand winding and thence over conductor H to This battery l0. Relays 6 and I will not lock up as ground is not applied to conductors 3 and 4. To these conductors there is applied a voltage from the batteries connected to sending relays SR; and SR; which is opposed to that of battery Hi. When relay 5 is operated the previously traced circuit for relay 8 is open and relay 8 releases. This opens the previously traced circuits for relays 5 and 1 and as they did not, lock up they will release. The locking up of relay 5 keeps repeater R1 disconnected from the hub circuit and removes the ground applied to the hub circuit by the opening of line L1. The release of relays 6 and l reconnects repeaters R2 and R3 to the hub circuit. Transmission may now be resumed between lines L2 and L3. After the line L1 has been repaired and the open removed, relay RR1 will operate. This will disconnect the ground from conductor 2 and open the previously traced locking circuit for relay 5 and its release will now reconnect line L1 to the hub circuit. The arrangements of the invention would operate in substantially a similar manner if either of lines L2 or L3 remained open for an appreciable length of time.

While the invention has been disclosed as embodied in certain specific forms which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is:

1. A telegraph system comprising a plurality of lines terminating at repeaters, a hub circuit for interconnecting said lines, a slow operate relay operated if one of said lines is disabled for an appreciable length of time, means controlled by the operation of said relay for automatically disconnecting said disabled line from said hub circuit and allowing transmission between the remaining lines to take place over said hub circuit.

2. A telegraph system comprising a plurality of lines terminating at repeaters, a hub circuit for interconnecting said lines, a slow operate relay connected to said hub circuit adjusted to be operated if one of said lines is disabled for an appreciable length of time, a series of relays each individual to a line, means controlled by the operation of said slow operate relay for operating all of said series of relays, means controlled by each of said series of relays for disconnecting its individual line from said hub circuit and releasing said slow release relay, and means for locking up the relay in said series which is individual to the line disabled.

3. A telegraph system comprising a plurality of lines terminating at repeaters, a hub circuit for interconnecting said lines, a slow operate relay connected to said hub circuit and adjusted to operate if one of said lines is disabled for an appreciable length of time, and means controlled by said relay for automatically momentarily disconnecting all of said lines from said hub circuit and causing the disconnection of said dis- 

